High thrust capacity shaft seal assembly for fuel pumps

Abstract

A shaft seal assembly (2) for a fuel pump includes a seal housing (4) attached to the fuel pump housing (6). A drive shaft (10) mounted for rotation in the fuel pump housing has a sealing face (14) which is engaged by a thrust face (42) of a thrust member (40) and by a seal face (18) of a carbon face seal (20). The thrust member and the carbon face seal are positioned with a steel carrier (26) mounted in the seal housing. A universal washer (32) is located between the carrier and the rear wall of the seal housing so that the carrier may undergo universal movement in response to movements of the thrust member. Misalignments between the axis of the shaft and the axis of the seal housing result in corresponding movements of the thrust member and the carrier which enable the axis of the face seal to remain aligned with the axis of the shaft. This arrangement permits the carbon face seal to be pressure balanced so that a relatively high fuel pressure surrounding the shaft will not produce unacceptable wear of the carbon face seal.

We claim: 
     
       1. In an improved shaft seal assembly for a pump having a pump housing and a drive shaft with a sealing face extending therein of the type comprising: a seal housing mounted upon the front of the pump housing in surrounding relationship to the drive shaft, a face seal, having its seal face in wiping engagement with the sealing face, mounted in the seal housing such that it is and capable of universal motion and wherein the improvement comprises: a thrust member having a thrust face mounted in the seal housing for universal motion with respect thereto and such that its thrust face engages the sealing face during normal pump operation;   means to prevent rotation of the thrust member with respect to the seal housing; and   means to transmit movements of the thrust member to the face seal such that misalignments between the seal housing and the axis of the drive shaft produce corresponding displacements in the axis of the face seal.   
     
     
       2. The improvement of claim 1, wherein the movement transmitting means comprises: a carrier mounted in the seal housing for universal motion, the thrust member and the face seal being mounted in the carrier in radially spaced relationship.   
     
     
       3. The improvement of claim 1, wherein the rotation preventing means comprises: a dowel mounted in the housing and extending through the carrier, the dowel being received by the thrust member in such a manner as to prevent any rotation thereof.   
     
     
       4. In an improved shaft seal assembly for a pump having a pump housing and a drive shaft with a sealing face extending therein of the type comprising: a seal housing mounted upon the front of the pump housing in surrounding relationship to the drive shaft, a face seal, having its seal face in wiping engagement with the sealing face, mounted in the seal housing such that it is and capable of universal motion wherein the improvement comprises: a thrust member having a thrust face mounted in the seal housing for universal motion with respect thereto and such that its thrust face engages the sealing face during normal pump operation;   means to prevent rotation of the thrust member with respect to the seal housing; and   the face seal being mounted in the seal housing such that it is in engagement with the thrust member whereby movements of the thrust member caused by misalignments between the seal housing and the axis of the shaft will produce corresponding displacements in the axis of the face seal.   
     
     
       5. The improvement of claim 4, wherein the face seal comprises: a purch seal; and wherein the improvement further comprises:   a universal washer mounted in the seal housing in engagement with the purch seal to permit universal motion of the purch seal and the thrust member.   
     
     
       6. The improvement of claim 4, wherein the face seal comprises: a carbon face seal; and wherein the improvement further comprises:   a spring washer mounted in the housing in engagement with the carbon face seal to urge the seal face into contact with the sealing face; and   the thrust member and the seal housing having engaged bearing surfaces shaped as spherical segments to permit movements of the thrust member caused by misalignments between the seal housing and the axis of the shaft.   
     
     
       7. A method of sealing the drive shaft of a pump having a pump housing and a seal housing mounted thereupon in which the drive shaft is mounted for rotation in the pump housing which comprises the steps of: engaging a sealing face on the drive shaft with a thrust member contained in the seal housing;   moving the thrust member when the axis of the seal housing and the drive shaft axis become misaligned so that the axis of the thrust member remains aligned with the axis of the shaft; and   transmitting movements of the thrust member to a face seal with a seal face in engagement with the sealing face such that the axis of the face seal remains aligned with the axis of the shaft.